The invention relates to a cutting tool according to claim 1, and particularly to a cutting tool comprising a first handle, a second handle, a first cutting blade fixedly attached to the first handle, as well as a second cutting blade fixedly attached to the second handle, the first and the second cutting blades being engaged with one another at a pivot point such that the first and the second cutting blades are movable in a scissor-like manner between an open position and a closed position in response to a relative rotational movement of the first and the second handles around the pivot point, and transmission means for transmitting power from the handles to the cutting blades. In the present context, cutting tool is used to refer to all cutting tools that produce a scissor-like movement. In the figures and the disclosed particular embodiment of the invention, the tool in question is hedge shears.
When hedge shears are used for cutting branches, the branches to be cut are gathered inside a sector defined by the cutting blades at the beginning of the cutting movement, when the cutting blades are in an open position. As the cutting movement progresses, most branches are cut using the outermost ends of the cutting blades, which is disadvantageous since at the outermost end of the cutting blades the cutting power is the lowest. Consequently, a user of the hedge scissors has to put in a greater effort in order to cut the branches by the outermost parts of the cutting blades. This results in inefficient cutting operation.
In most known devices, the cutting power remains constant over the entire cutting distance between the open position and the closed position. Thus, the cutting power remains the same between the beginning of the cutting movement, where the branches are gathered inside a sector between the cutting blades, and the end of the cutting movement, where the actual cutting takes place. Hence, the cutting movement is inefficient, since the process of gathering the branches inside the sector defined by the cutting blades requires considerably less power than that of actually cutting the branches.
Transmission and linkage systems are widely used in various cutters to enhance the cutting power. This often leads to an increased movement of the handles, which compels the user to take a wider grip than would otherwise be necessary. Although most cutters are capable of increasing the cutting power, they still produce a constant-remaining increased cutting force. However, systems also exist which produce a progressive cutting force, one such system being disclosed in European Patent No. 1 153 713 granted to the applicant, the publication disclosing hedge shears that are capable of producing a progressive cutting force. In these hedge shears, the transmission mechanism is provided such that the greatest force is produced when it is needed, i.e. towards the end of the cutting movement. This aforementioned patent discloses hedge shears comprising two pairs of inter-engaging toothed transmission parts in order to produce an increasing cutting force. These hedge shears comprise a first and a second handle, the first handle comprising a first handle transmission part and the second handle comprising a second handle transmission part. The hedge shears also comprise a first and a second cutting blade, the first cutting blade containing a first blade transmission part and the second cutting blade containing a second blade transmission part. The first and the second handle transmission parts as well as the first and the second blade transmission parts are mutually symmetrical. The hedge shears also comprise means for attaching the first handle to the first cutting blade and for attaching the second handle to the second cutting blade and means for attaching the first blade pivotally to the second cutting blade. In such a case, the teeth of the first handle transmission intermesh with the teeth of the first blade transmission and the teeth of the second handle transmission intermesh with the teeth of the second blade transmission in order to increase the cutting force when the blades move towards the closed position.
A problem with the above-described arrangement is that at least one of the transmission means are formed directly in a blade, which means that they are made of the same material as the blade. The blade, in turn, is most usually made of metal, which means that the transmission means provided in the blade are made of metal. It is a laborious procedure to work metal in order to provide such transmission means and, besides, metal is an expensive material, so transmission means, and thus hedge shears, are expensive to manufacture. Furthermore, transmission means formed directly in the blade easily allow branches to enter between the teeth of the transmission means during the cutting operation, which hinders or even prevents operation of the hedge shears.